added feature to render and play audio/* mime type mms attachments

satisfies main request in #159

works for both received and sent audio attachments - even though you can't send them.... yet

for a plain audio attachment file a small player will be shown with play/pause toggle button and a draggable seek bar (and a sound wave graphic thingy so that it's easy to spot that its an audio file). if the file has embedded title meta-data (ie title id3 tag) it will also be shown;

if the title is too long to fit in it's box it will marquee while the file is being played.

if the audio attachment file has an embedded image (ie id3 cover art in an mp3) the image will also be displayed and the player goes square to contain the album art;